This invention relates to planetary transmissions and, more particularly, to planetary transmissions having three planetary gearsets that are controlled to establish at least seven forward speed ratios and one reverse speed ratio.
Automatic shifting power transmissions are currently used in a majority of the vehicles produced in the United States. These vehicles generally employ three- and four-speed power transmissions. More recently, a trend towards more ratios, such as five- and six-speed power transmissions, has been proposed. In fact, some manufacturers do provide five-speed transmissions. Many of the vehicles utilizing manual type transmissions or countershaft type transmissions employ five- and six-speed power transmissions.
The five- and six-speed power transmissions provide improved vehicle acceleration performance and fuel economy when compared with three- and four-speed transmissions. Seven-speed transmissions offer further vehicle acceleration performance and fuel economy over five- and six-speed transmissions. However, seven-speed power transmissions have not been proposed due to the complexity of these assemblies, as well as size and cost. There are many current patents that describe five- and six-speed power transmissions. Some of the six-speed power transmission patents, especially those assigned to the assignee of the present invention, describe six-speed power transmissions in families, wherein one or more family members incorporate a seven-speed power transmission.
It is an object of the present invention to provide an improved family of multi-speed planetary transmissions having three planetary gearsets and providing at least seven forward speed ratios and one reverse speed ratio.
In one aspect of the present invention, each of the planetary gearsets has first, second, and third members.
In another aspect of the present invention, an interconnecting member continuously interconnects the first member of the first planetary gearset with a first member of the second planetary gearset.
In yet another aspect of the present invention, a second fixed interconnection continuously interconnects a second member of the first planetary gearset with a second member of the second planetary gearset.
In yet still another aspect of the present invention, a third fixed interconnecting member continuously interconnects a first member of the third planetary gearset with one of the members of the second or first planetary gearset.
In still another aspect of the present invention, a member of the first planetary gearset is continuously connected with a stationary member, such as a transmission housing.
In a yet still another aspect of the present invention, the output of the transmission is continuously interconnected with at least one member of one of the planetary gearsets, and the input shaft is only selectively connectible with members of the planetary gearsets through selectively engageable torque transmitting mechanisms.
In yet another aspect of the present invention, the planetary transmission has six torque-transmitting mechanisms, at least two of which selectively interconnect the input shaft of the transmission with members of the planetary gearsets.
In a further aspect of the present invention, a third of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with either the input shaft, the output shaft, or another member of one of the planetary gearsets.
In a yet further aspect of the present invention, a fourth of the of the torque-transmitting mechanisms selectively interconnects a member of at least one of the planetary gearsets with the output shaft, or another member of one of the planetary gearsets.
In a still further aspect of the present invention, a fifth of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with another member of one of the planetary gearsets.
In a yet still further aspect of the present invention, a sixth of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with either the output shaft, another member of one of the planetary gearsets, or with the stationary transmission member.
In still a further aspect of the present, the six torque-transmitting mechanisms are selectively engageable in combinations of two to establish at least seven forward speed ratios and one reverse speed ratio between the input shaft and the output shaft of the transmission.
The present invention provides a family of low mechanical content seven speed power transmissions. These transmissions have only three planetary gearsets and six selectively engageable torque-transmitting mechanisms, which may be comprised of six clutches or five clutches and one brake. Each of the planetary gearsets has three members comprised of a sun gear member, a ring gear member, or a planet carrier assembly member. Each planet carrier assembly member can be of either the single pinion type (simple) or of the double pinion type (compound).
The six torque-transmitting mechanisms are arranged to provide interconnections between the planetary gearset members or between the input shaft or transmission housing and the planetary gear members. By engaging these torque-transmitting mechanisms in combinations of two, the three planetary gearsets will provide at least seven forward speed ratios and one reverse speed ratio between the input shaft and the output shaft of the transmission.